Textural and genetic investigations of gold mineralization in fault-controlled quartzcarbonate veins in Bayburt-Zarani area (Eastern Pontides-NE Turkey)

Abstract

: The Eastern Pontides Orogenic Belt (EPOB), geographically corresponding to the northeastern part of Turkey hosts several different types of mineralizations that are closely related to Late Mesozoic-Early Cenozoic arc magmatism. Of these, Zarani gold mineralization, which is located in the southern part of the EPOB occurs as quartz-carbonate veins/veinlets within the Pulur metamorphic massif of Paleozoic age. Mineral textures indicate low-temperature vein-type mineralization. Gold mainly occurs in quartz and pyrite. The presence of calcite, dolomite, and sericite in the mineralization indicates near neutral pH conditions of ore-forming fluid. Geochemical analyses of chlorites in the quartz-carbonate veins reveal a temperature of ore formation at 140–297 °C, which is compatible with those obtained from fluid inclusions in the mineralized quartz (i.e. 132–226 °C). The average salinity value obtained from fluid inclusions is 4.32% NaCl equiv. O and H isotope values range from –6.03‰ to +1.47‰ and from –60‰ to –119‰, respectively, indicating a mixture of magmatic and meteoric fluids. Mixing is also evidenced by the X Fe analytical data of hydrothermal chlorites associated with ore-forming gangue minerals. Gold precipitation in Zarani mineralization is caused by boiling. The occurrence of mineralization within quartz-carbonate vein/veinlets in metamorphic host rocks, the mineral paragenesis with near-neutral pH conditions of the ore-forming low salinity fluids and the H–O isotopic data imply that the Zarani gold mineralization is an orogenic type epithermal mineralization that may be related to deeply buried Early Cenozoic felsic intrusions, produced by subduction-induced processes in the southern part of the EPOB.